1. Field of the Invention
The present invention pertains to oil/water separators and, more specifically, to a system whereby such separation is accomplished by aeration as the fluid circulates through a series of interconnected flotation cells.
2. General Background
Oil/water separators have been widely used in the oil and gas industry, pulp and paper mills, municipal waste treatment facilities, and meat packing plants to name a few. There are many varieties ranging from the single cell assemblies to the multi-stage devices.
A typical version of the single cell assembly is disclosed in U.S. Pat. No. 3,986,954 to George, et al. This assembly incorporates a single U-shaped tank through which the fluid to be treated passes. A gas stream is injected into this tank and percolates through this fluid while the pressure of the fluid is increased. After such pressure is released, the gas breaks out of solution and attaches itself to any contaminants in the fluid, thereby separating these contaminants from the fluid.
Typical examples of multi-stage devices are disclosed in U.S. Pat. No. 4,226,706 to Degner, et al.; U.S. Pat. No. 4,564,457 to Cairo, Jr., et al.; and, U.S. Pat. No. 4,824,579 to George. Each of these devices incorporates a large tank that has been sub-divided into a series of smaller cells through which the fluid passes. Each cell is in open communication with it adjacent cell with each such cell having its own aeration system. In this manner, as the fluid flows from one cell to the next, it gradually becomes cleaner and clearer. In some cases, skimmer paddles are used to remove the aerated contaminants, in others, a central channel is employed to remove them.
In view of the above, it is an object of this invention to provide an improved multi-stage apparatus for separating oil and other contaminants from a fluid. Another object of this invention is to provide a means for separating such contaminants without the need for skimmer paddles and without a central channel. A further object of this invention is to begin the separation process prior to the introduction of the fluid to the first cell. Still another object of this invention is to provide a means of individually varying the amount of contaminants that are removed from each of the cells. Yet another object is to provide a means of transferring fluid between the individual cells which enhances the separation of the oil and/or solid contaminants from the fluid. These and other objects of this invention will become obvious upon further investigation.